(a) Field of the Invention
The present invention relates to a base member for swivel caster, and particularly to a base member for swivel caster which swivels and rotates freely.
(b) Description of the Prior Art
As shown in FIG. 5, a conventional base member for swivel caster comprises a fixed base 10, a rotation base 20, and a plurality of rolling balls 30 loaded between the fixed base 10 and the rotation base 20. The fixed base 10 forms a plurality of assembling holes 101 through outward surface thereof. During assembly, the rolling balls 30 are extended through the assembling holes 101 and loaded between the fixed base 10 and the rotation base 20. Then the assembling holes 101 are blocked with fixed elements 40, whereby the rolling balls 30 are retained firmly. This design is disclosed in U.S. Pat. Nos. 4,316,305, 5,983,451, etc.
However, pressure of the fixed elements 40 with respect to the assembling holes 101 is uneasily controlled so that the rolling balls 30 fail to rotate freely especially when they rotate about the fixed elements 40. It is desired to overcome this defect.